1. Field of the Invention
The present invention relates to an apparatus for stopping an engine having a fuel injection pump.
2. Description of the Prior Art
Referring to FIG. 1 showing a known type of engine stop apparatus, an electromagnetic selector valve 1 is designed so that when an engine is in operation, a fuel tank 2 is connected to an inlet 3a of a fuel supply pump 3 and a fuel injection pump 4 is connected to an outlet 3b of the fuel supply pump 3 as shown in the Figure. During the stopping operation, the electromagnetic selector valve 1 connects the fuel injection pump 4 to the inlet 3a of the fuel supply pump 3 and the outlet 3b of the fuel supply pump 3 to the fuel tank 2. Numeral 5 designates a fuel injection nozzle, 6 a fuel filter, and 7 to 11 fuel lines. In this way, with the engine in operation, the fuel supply pump 3 supplies the fuel to the fuel injection pump 4 from the fuel tank 2 to thereby continue the engine operation, and during the stopping operation of the engine the fuel is returned to the fuel tank 2 from the fuel chamber (not shown) of the fuel injection pump 4 so that the fuel injection from the fuel injection pump 4 is stopped and the engine is stopped. In this case, while the electromagnetic selector valve 1 may be replaced with any type other than the electromagnetic type, it is the usual practice to use an electromagnetic valve for the selectro valve 1 in cases where the engine is automatically stopped by simply turning the key switch off or any malfunction of the engine such as the reverse operation is automatically detected to automatically stop the engine.
In the case of large engines, however, due to the high rate of fuel flow as well as the restrictions imposed by the cross-section area of the flow passages, the electromagnetic selector valve 1 must have a stroke of about 10 mm if it is of the spool valve type or a rotational angle of over 45.degree. if it is of the rotary valve type. Thus, in this case a large value is required for the output of the actuator (solenoid) of the electromagnetic selector valve 1 and the actuator must be increased in size and current consumption (over 10 A).
In the case of Diesel engines, with the engine at rest the electromagnetic selector valve 1 must always be held in the stop position due to the existence of a problem that unless the fuel supply is cut off when the engine is at rest, there is the danger of the engine being automatically started by an external force (e.g., due to a rear-end collision or downward movement along a slope). Thus there is a disadvantage that the actuator of the electromagnetic selector valve 1 must always be energized either while the engine is in operation or at rest, with the result that if the valve 1 is designed so as to energize the actuator while the engine is at rest, there is the danger of causing the battery to run down, and if it is designed to energize the actuator while the engine is in operation, the actuator must be increased in size to prevent the generation of heat therein and the use of a high-output generator is also required.